Abstract
The 1,6- and 1,7-regioisomers of dinitro- (1,6-A and 1,7-A) and diamino-substituted perylene bisimides (1,6-B and 1,7-B), and 1-amino-6-nitro- and 1-amino-7-nitroperylene bisimides (1,6-C and 1,7-C) were synthesized. The 1,6-A and 1,7-A regioisomers were successfully separated by high performance liquid chromatography and characterized by 500 MHz 1H-NMR spectroscopy, and subsequently, their reduction which afforded the corresponding diaminoperylene bisimides 1,6-B and 1,7-B, respectively. On the other hand, the monoreduction of 1,6-A and 1,7-A, giving the asymmetric 1-amino-6-nitro (1,6-C) and 1-amino-7-nitroperylene bisimides (1,7-C), respectively, can be performed by shortening the reaction time from 6 h to 1 h. This is the first time the asymmetric 1,6-disubstituted perylene bisimide 1,6-C is obtained in pure form. The photophysical properties of 1,6-A and 1,7-A were found to be almost the same. However, the regioisomers 1,6-C and 1,7-C, as well as 1,6-B and 1,7-B, exhibit significant differences in their optical characteristics. Time-dependent density functional theory calculations performed on these dyes are reported in order to rationalize their electronic structure and absorption spectra.
Highlights
The chemical structures of symmetric (1,6-A, 1,7-A, 1,6-B, and 1,7-B) and asymmetric Perylene bisimides (PBIs) (1-A, 1-B, 1,6-C, and 1,7-C) and their synthetic routes are shown in Scheme 1
The mononitration can be achieved by a reaction of perylene bisimide (PBI) with cerium (IV) ammonium nitrate (CAN) and HNO3 under ambient temperature for 2 h, giving 1-A in high yields of ca. 95%
Further nitration of 1-A using the same reagents at ambient temperature for 46 h gave dinitroperylene bisimides in 80% yield
Summary
Perylene bisimides (PBIs) and their related derivatives have received considerable attention due to their potential applications in molecular electronic and optical devices, such as light-emitting diodes [1,2,3,4], organic field-effect transistors (OFETs) [5,6,7,8,9,10], light-harvesting arrays [11,12], photovoltaic cells [13,14,15,16,17,18,19,20,21,22], LCD color filters [23,24], photochromic materials [25,26], and molecular wires [27,28]. PBIs have been utilized as building blocks to construct supramolecular or artificial photosynthetic systems [29,30,31] These compounds are advantageous due to their high molar absorptivities, excellent thermal and optical stabilities, ease of synthetic modification and reversible redox properties [32,33,34,35,36,37,38,39,40,41,42]. The electronic characteristics of PBIs can be fine-tuned by the substitution of the conjugated aromatic core Based on this concept, more and more perylene bisimide derivatives with either electron-donating or electron-withdrawing groups have been reported in the literature, including: (a) piperidinyl-substituted.
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